AIX

i am new in the field 3months to be precise. how do i come up with size, i want to change for the filesystem? assuming there is enough space on the volume group.
do i just assign any value?

2 ways:
a) Read the man pages : man chfs
Your interested in -a size=....
b) use smit/smitty -> smitty chfs, but in your case look around starting with smitty lvm

Good luck

thanks, but this will just effect the file size change not tell you how to come up with the size

The best for you is to see how LVM works...
So a good exercice would be to create a filesystem then try to extend reduce etc...

1) lsvg -o to see what currently active group you have
choose one and look if you have enough free PP to experiment:
lsvg <volgroup>
lsvg -p <volgroup>
lsvg -l <volgroup>

then smitty LVM... create your logical volume, use it for a JFS2 etc...

I could recommend a tutorial to you that might help a lot to get acquainted with AIX: From New User to Technical Expert

thanx for ur response the tutorial is really helpful